Could 'Superhurricanes' Have Done in Dinosaurs?

Article excerpt

North Americans and Caribbean islanders have been having a vigorous hurricane season with more Atlantic tropical storms already named than have ever been listed before.

But what they've seen is mild compared with the storminess that dinosaurs may have faced when they faded out 65 million years ago. Superstorms stirred up by asteroids or intensive submarine volcanism may have nudged the beasts toward the exit.

That's the conclusion that emerges from computer simulations run by Richard Rotunno of the National Center for Atmospheric Research in Boulder, Colo., Kerry Emanuel of the Massachusetts Institute of Technology, and several colleagues. They've been playing an intellectual game that exercises both the computer model and their own understanding of how hurricanes work.

In a hurricane, billowing cumulus clouds pump heat and water vapor from the sea surface high into the atmosphere. Many hurricane studies focus on this action. But Dr. Rotunno explains that he and Dr. Emanuel think the interaction between the hurricane vortex and the sea surface is the key to how these great storms grow and intensify. Their computer simulations show that the warmer the sea surface is, the more intense are the storms that may develop.

Could this have a bearing on mass extinctions in the past? Some extinctions wiped out the majority of then-living species. For example, about 96 percent of all species in the fossil record around 245 million years ago vanished. Many scientists have suggested that massive volcanism or an incoming asteroid may have thrown up dust veils that blocked sunlight long enough to disrupt plant-based food chains.

Rotunno and Emanuel doubt such events could pollute the stratosphere long enough to affect global climate on the scale needed for mass extinctions. …